Management of an optical network is usually performed based on monitoring various specific parameters of the network operation.
For example, US2003016695A describes a method and apparatus for maintaining an established error count for data transmitted on a WDM optical communication network. Error counts from an FEC code are monitored and operational parameters are automatically adjusted in response to the error counts, thereby achieving system optimization in an automated manner.
Digital communication is based on distinguishing different levels of optical or electrical signals; owing to that, proper selection of a decision threshold is very important for operation of a network. Usually, it is a binary decision threshold for On-Off Keying modulation format, but the problem is actual also for multiple level decision thresholds of M-ary modulation formats. A number of sources in the prior art propose performing adaptation of binary threshold's decision level in optical network elements, mainly in receivers.
U.S. Pat. No. 7,269,347 B describes a method of controlling an optical signal receiver that utilizes three control loops: a first control loop tunes the decision threshold of the receiver when the optical network is in a substantially steady state and a second control loop rapidly switches to a reference decision threshold upon the occurrence of an alarm condition. The invention rapidly switches to a predetermined reference decision threshold to compensate for optical signal changes in eye diagram and received power after a protection switch or traffic reroute. After a protection switch, a slower tuning algorithm is used to adjust the decision threshold to a more optimum value. In the third control loop, the optical signal receiver may utilize a peak detector that detects the optical signal peak and a potentiometer that is commanded by a controller to output a commanded percentage of this peak value to adjust the threshold and to thereby respond to transients.
Prior art comprises some discussions about arranging feedback from the changing threshold itself.
For example, U.S. Pat. No. 6,580,763 describes controlling the decision threshold and the sampling instant of a data regenerator wherein the data regenerator includes a second data path whose decision threshold can be shifted. By comparing the output data, it is possible to calculate the bit errors which are caused by a shifting of the decision threshold. By experimentally shifting the sampling instant and subsequently the decision threshold the optimal sampling instant and the optimal decision threshold are found.
US 20090269076 describes systems and methods for a receiver threshold optimization loop to provide self-contained automatic adjustment in a compact module, such as a pluggable optical transceiver. The receiver threshold optimization loop utilizes a performance metric associated with the receiver, such as FEC, to optimize performance of the receiver. The receiver is optimized through a change in the receiver threshold responsive to the performance metric. Further, US 20090269076 provides improved receiver performance through a continuous adjustment that is self-contained within the receiver, such as within a pluggable optical transceiver compliant to a multi-source agreement (MSA). The receiver threshold optimization loop can include a fine and a coarse sweep of adjustment from an initial setting.